ANAPTYCHUS, RIIYNCIIOLITES, ETC. 260 



specimen with (loniatites. Nearly fifty varieties liave ])vva\ 

 described. 



Meyer considered them bivalve shells, and described them 

 under the name of Aphjclius : Deslongchamps with the same im- 

 pression, called them Mimsteria : d'Orbigny thought them plates 

 of cirrii)edes, and DesJiays believed them to be the gizzards of 

 Ammonites ; Coquand compared them with Teudoi^sis, and they 

 certainly resemble in some degree that genus, as well as Belo- 

 feuthis, Bidemnoifepia^ etc. 



A. LAMELLOSUS, Park. PI. 104, tig. 578. Oxford Clay, Solen- 

 hofen. 



T. LATUS, Brown. PI. 104, llg, 575 a. 



Trigonelletes associated with an Ammonite. PI. 104, fig. 574. 



Genus Anaptychus, Oppel. Horny and flexible, in a single 

 piece. 



Associated with the Ariefes group of Ammonites. 

 Ana})tychus of Ammonites costatus. PI. 104, figs. 575, 576. 



Beaks of TETRAKRANcniATES. 



These are found associated with fossil Nautili and occasionally 

 Belemnites, but never with Ammonites. The upper beaks have 

 been described under the name of Bhyncholites, the lower 

 ones as Conchorhynchus. 



R. AsTiERiANA, d'Orb. PL 104, fig. 577. 



C. AViROSTRis, Bronn. PL 104, fig. 978. 



C. OwENii, Bronn. PL 104, fig. 579. 



Peltarion, Deslongchamps. This was formerly believed to 

 l)e the mandibular armature of tetrabranchiates, consisting of 

 circular or transversely-oval calcareous plates, with rounded 

 anterior and produced and truncated posterior margins. Through 

 the researches of M. Crosse (Jour, de Gonch.^ 3 ser., xv 57, 

 1875), there is no doubt that these Peltaria? are opercula of 

 fossil species of JVeritopsis ; they resemble the operculum of the 

 recent N. radula. 



Several species haA'e been described from U. Lias to Coral- 

 line Rag. 



